Exposure apparatus having reaction frame

ABSTRACT

A guideless stage for aligning a wafer in a microlithography system is disclosed, and a reaction frame is disclosed which isolates both external vibrations as well as vibrations caused by reaction forces from an object stage. In the guideless stage an object stage is disclosed for movement in at least two directions and two separate and independently movable followers move and follow the object stage and cooperating linear force actuators are mounted on the object stage and the followers for positioning the object stage in the first and second directions. The reaction frame is mounted on a base structure independent of the base for the object stage so that the object stage is supported in space independent of the reaction frame. At least one follower is disclosed having a pair of arms which are respectively movable in a pair of parallel planes with the center of gravity of the object stage therebetween. The linear positioning forces of the actuator drive means are mounted and controlled so that the vector sum of the moments of force at the center of gravity of the object stage due to the positioning forces of the drive means is substantially equal to zero. The actuator mounting means can include at least two thin flexible members mounted in series with the primary direction of flex of the members being orthogonal to one another.

This is a division of application Ser. No. 09/127,288, filed Jul. 31,1998, which in turn is a continuation of application Ser. No.08/627,824, filed Apr. 2, 1996, now U.S. Pat. No. 5,942,871, which is acontinuation of application Ser. No. 08/221,375, filed Apr. 1, 1994, nowU.S. Pat. No. 5,528,118.

FIELD OF INVENTION

The present invention relates, in general, to electro-mechanicalalignment and isolation and, more particularly, to such method andapparatus for supporting and aligning a wafer in a microlithographicsystem and isolating the system from its own reaction forces andexternal vibrations.

BACKGROUND OF THE INVENTION

Various support and positioning structures are known for use inmicrolithographic instruments. Typically, in the prior art, XY guides,including a separate X guide assembly and Y guide assembly, are utilizedwith one guide assembly mounted on and movable with the other guideassembly. Often, a separate wafer stage is mounted on top of these guideassemblies. These structures require high precision and many parts.Typically, external forces directed to parts of the positioning assemblyand reaction forces due to movement of different parts of the assemblyare coupled directly to the image forming optics and reticle handlingequipment resulting in unwanted vibration.

U.S. Pat. No. 5,120,036 to Van Engelen et al. describes a two-steppositioning device using Lorentz forces and a static gas bearing for anopto-lithographic device.

U.S. Pat. No. 4,952,858 is directed to a microlithographic apparatusutilizing electro-magnetic alignment apparatus including a monolithicstage, a sub-stage and isolated reference structure in which forceactuators imposed between the monolithic stage and the sub-stage areused for suspending and positioning monolithic stage in space. In thisapparatus a Y frame or stage is mounted on an X frame and the monolithicstage is positioned from and supported in space from the Y frame.

SUMMARY OF THE INVENTION

Broadly stated, the present invention is directed to method andapparatus utilizing a guideless stage for supporting an article andincorporating a reaction frame which isolates both external forces aswell as reaction forces created in moving the object from other elementsof the system such as a lens system which produces an image that isexposed on the photoresist of a wafer object surface.

The present invention incorporates an object stage, a reaction framemounted on a base and substantially free from transferring vibrationsbetween itself and the object stage, means for supporting the objectstage in space independent of the reaction frame and cooperating forcetype linear actuator means mounted on the object stage and the reactionframe for positioning of the object stage. The object stage can bemounted for movement in a given direction or can constitute a XY, stagefor movement in the X and Y directions while being supported in space inthe Z direction.

A feature, an advantage of this invention is the provision of a support,positioning and isolation assembly which allows the positioning functionof the object or wafer stage to be accomplished while minimizingvibrations coupled to the stage and lens systems from the reaction stagefaster and with fewer parts while minimizing vibrations coupled to thestage and isolating the stage from undesired reaction forces.

In accordance with another aspect of the present invention, apositioning method and apparatus are provided for an XY stage with anindependently moveable X follower and independently moveable Y followerand cooperating linear force actuators mounted between the stage andfollowers whereby the movement of either follower does not effect themovement of the other follower.

Another aspect of this invention is the provision on at least onefollower of a pair of arms on the follower with each arm supporting adrive member and wherein the arms are positioned and movable in spacedapart planes above and below the center of gravity of the object stage.

In accordance with another aspect of the present invention, theguideless stage incorporates at least three linear force actuators withtwo of those actuators driving in one of the X or Y directions and thethird actuators driving in the other of the X and Y directions. Inaccordance with the preferred embodiment of this invention the guidelessstage incorporates at least four linear actuators operating between theXY stage and a reaction frame assembly with each actuator including adrive member on the XY stage so that a pair of X drive members serve todrive the XY stage in an X direction and a pair of Y drive members serveto drive the XY stage in the Y direction. The linear actuators and theirdrive members are constructed, positioned and controlled such that thevector sum of the moments of force at the center of gravity of the XYstage due to the positioning forces of cooperating drive members issubstantially equal to zero.

These features and advantages of the present invention will become moreapparent upon perusal of the following specification taken inconjunction with the following drawing wherein similar characters ofreference refer to similar parts in each of the several views.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a microlithography system incorporatingthe present invention.

FIG. 1A is a view of a portion of the structure shown in FIG. 1delineated by line A—A and with the reaction stage which is shown FIG. 1removed.

FIG. 1B is an elevational view, partially in section, of the structureshown in FIG. 1.

FIG. 1C is a schematic elevational view, partially in section, of theobject positioning apparatus of the present invention.

FIG. 2 is a plan view of the wafer XY stage position above the reactionstage.

FIG. 3 is a side elevational view of a portion of the structure shown inFIG. 2 taken along line 3—3 in the direction of the arrows.

FIG. 3A is an enlarged view of a portion of the structure shown in FIG.3 delineated by line B—B.

FIG. 4 is a perspective view of the reaction stage showing the XYfollowers without the means for coupling to the XY stage for positioningof the XY stage.

FIG. 4A is an enlarged perspective view of the XY followers illustratedin FIG. 4.

FIG. 5 is a schematic block diagram of the position sensing and controlsystem for the preferred embodiment of this invention.

FIGS. 6 and 7 are views similar to FIGS. 2 and 3 of an alternativeembodiment of the present invention.

FIGS. 8 and 9 are views similar to FIGS. 2 and 3 of still anotherembodiment of the present invention.

FIG. 10 is an enlarged top view of a portion of the structure shown inFIG. 8.

FIG. 11 is an end view of the structure shown in FIG. 10 taken alongline 11—11 in the direction of the arrows.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

While it will be appreciated by those skilled in the art that theguideless stage, with or without its isolating reaction frame, has manyapplications to many different types of instruments for precisepositioning of objects, the present invention will be described withrespect to a preferred embodiment in the form of a microlitholigraphicinstrument for aligning wafers in a system where a lens produces animage which is exposed to the photoresist on the wafer surface. Inaddition, while the guideless stage with or without its isolation stagecan be utilized as a guideless object stage movable in just onedirection, such as a X or a Y direction, the preferred embodiment isdirected to a guideless XY wafer stage as described below.

Referring now to the drawings, with particular reference to is FIGS. 1and 2, there is shown a photolithographic instrument 10 having an upperoptical system 12 and a lower wafer support and positioning system 13.The optical system 12 includes an illuminator 14 including a lamp LMP,such as a mercury lamp, and an ellipsoid mirror EM surrounding the lampLPM. And the illuminator 14 comprises optical integrator such as a fly'seye lens FEL producing secondary light source images and a condenserlens CL for illuminating a reticle (mask) R with uniformed light flux. Amask holder RST holding the mask R is mounted above a lens barrel PL ofa projection optical system 16. The lens barrel PL is fixed on a part ofa column assembly which is supported on a plurality of rigid arms 18each mounted on the top portion of an isolation pad or block system 20.

Inertial or seismic blocks 22 are located on the system such as mountedon the arms 18. These blocks 22 can take the form of a cast box whichcan be filled with sand at the operation site to avoid shipment of amassive structure. An object or wafer stage base 28 is supported fromthe arms 18 by depending blocks 22 and depending bars 26 and horizontalbars 27 (see FIG. 1A). FIG. 1B is an elevational view, partially insection, of the structure shown in FIG. 1 except that in FIG. 1B Blocks22 are shown as being a different configuration than in FIG. 1 and 1A.

Referring now to FIGS. 2 and 3, there are shown plan and elevationalviews, respectively, of the wafer supporting and positioning apparatusabove the object or wafer stage base 28 including the object or wafer orXY stage 30 and the reaction frame assembly 60. The XY stage 30 includesa support plate 32 on which the wafer 34, such as a 12 inch wafer, issupported. The plate 32 is supported in space above the object stagebase 28 via vacuum pre-load type air bearings 36 which can be controlledto adjust Z, i.e., tilt roll and focus. Alternatively, this supportcould employ combinations of magnets and coils.

The XY stage 30 also includes an appropriate element of a magneticcoupling means such as a linear drive motor for aligning the wafer withthe lens of the optical system 16 for precisely positioning an image forexposure of a photoresist on the wafer's surface. In the embodimentillustrated, the magnetic coupling means takes the form of a pair ofdrive members such as X drive coils 42X and 42X′ for positioning the XYstage 30 in the X direction and a pair of Y drive members such as drivecoils 44Y and 44Y′ for positioning the XY stage 30 in the Y direction.The associated portion of the magnetic coupling means on the reactionframe assembly 60 will be described in later detail below.

The XY stage 30 includes a pair of laser mirrors 38X operative withrespect to a pair of laser beams 40A/40A′ and 38Y operative with respectto a pair of laser beams 40B/40B′ of a laser beam interferometer system92 for determining and controlling the precise XY location of the XYstage relative to a fixed mirror RMX at the lower part of the lensbarrel PL of the projection optical system 16.

Referring to FIGS. 4 and 4A, the reaction frame assembly 60 has areaction frame 61 which includes a plurality of support posts 62 whichare mounted on the ground or a separate base substantially free fromtransferring vibrations between itself and the object stage.

The reaction frame 61 includes face plates 64X and 64X′ extendingbetween support posts 62 in the X direction and 66Y and 66Y′ extendingbetween support posts in the Y direction. Inside the face plates 64-66 aplurality of reaction frame rails 67-69 and 67′-69′ are provided forsupporting and guiding an X follower 72 and a Y follower 82. Inside faceplate 64X are an upper follower guide rail 67 and a lower follower guiderail 68 (not shown) and on the inside surface of the opposite face plate64X′ are upper and lower follower guide rails 67′ and 68′. On the insidesurfaces of each of the face plates 66Y and 66Y′ is a single guide rail69 and 69′, respectively, which is positioned vertically in between theguide rails 67 and 68.

The X follower includes a pair of spaced apart arms 74 and 74′ connectedat their one end by a cross piece 76. Drive elements such as drivetracks 78 and 78′ (see FIG. 2) are mounted on the arms 74 and 74′,respectively, for cooperating with the is drive elements 42X and 42X′ ofthe XY stage. Since in the illustrated embodiment the drive elements 42Xand 42X′ on the XY stage are shown as drive coils, the drive tracks onthe X follower 72 take the form of magnets. The coupling elements couldbe reversed so that the coils would be mounted on the X follower and themagnets mounted on the XY stage. As the XY stage is driven in the X andY direction, the laser interferometer system 92 detects the new positionof the XY stage momentarily and generates a position information (Xcoordinate value). As described in greater detail below with referenceto FIG. 5 a servo position control system 94 under control of a hostprocessor (CPU) 96 controls the position of the X follower 72 and the yfollower 82 in response to the position information from theinterferometer system 92 to follow the XY stage 30 without anyconnection between the drive coils 42X,42X′ and the tracks 74,74′.

For movably mounting the X follower 72 on the reaction frame 61, theends of the arms 74 and 74′ at the side of the reaction frame 61 ride orare guided on the rail 69, and the opposite ends of the arms 74 and 74′ride on rail 69′ adjacent face plate 66 Y′. For moving the X follower 72a drive member 77 is provided on the cross piece 76 for cooperating withthe reaction frame guide 69 for moving the follower 72 in a directionwhich is perpendicular to the X direction of the XY stage. Since theprecision drive and control takes place in the XY stage 30, thepositioning control of the X follower 72 does not have to be as accurateand provide as close tolerances and air gaps as the XY stage 30.Accordingly, the drive mechanism 77 can be made of a combination of ascrew shaft rotated by a motor and a nut engaged by the X follower 72 ora combination of a coil assembly and a magnet assembly to establish alinear motor and each combination can be further combined with a rollerguiding mechanism.

Similar to the X follower 72, the Y follower 82 includes a pair of arms84 and 84′ connected at their one end by a crossbar 86 and includingdrive tracks 88 and 88′ for cooperating with the Y drive members 44Y and44Y′. The arms 84 and 84′ of the Y follower 82 are guided on separateguide rails. The ends of arm 84 ride or are guided on the upper rails 67and 67′ and the ends of arm 84′ are guided on lower rails 68 and 68′. Adrive mechanism 87 is provided on the cross piece 86 of the Y follower82 for moving the Y follower 82 along guides 67, 67′, 68 and 68′ betweenthe face plates 66Y and 66Y′ in a direction perpendicular to the Ydirection of the XY stage.

As best illustrated in FIG. 4A, the arms 74 and 74′ and crossbar 76′ ofthe X follower 72 all lie within and move in the same plane crossing theZ axis. The center of gravity of the XY stage 30 lies within or isimmediately adjacent to this plane. In this construction the driveforces from each of the drive coils 42X and 42X′ are in a directionalong the length of the arms 74 and 74′, respectively. However, the arms84 and 84′ of the Y follower 82 lie within and move in differentparallel planes spaced apart along the Z axis from one anotherrespectively above and below and parallel to the plane containing the Xfollower 72. In the preferred embodiment, the crossbar 86 lies in thelower plane containing the arm 84′ and a spacer block 86′, is positionedbetween the overlapping ends of the arm 84 and crossbar 86 to space thearms 84 and 84′ in their respective parallel planes. As with X follower72, the drive forces from each of the drive coils 44Y and 44Y′ are in adirection along the length of the arms 84 and 84′. Also, predeterminedgaps in X and Z directions are maintained between the drive coils44Y(44Y′) and the drive tracks 88(88′) to achieve the guideless concept.

In operation of the guideless stage and isolated reaction frame of thepresent invention, the XY stage 30 is positioned in an initial positionrelative to the projection lens as sensed by the interferometer system92, and the XY stage 30 is supported in the desired Z direction from theobject stage base 28 by the air bearings 36 with the drive coils 42X,42X′, 44Y and 44Y′ spaced from the drive elements in the form of drivetracks 78, 78′, 88 and 88′, respectively. There is no direct contactbetween the XY stage 30 and the reaction frame 61. That is, there is nopath for the vibration of the reaction frame to affect the position ofthe XY stage and vice versa. There is only indirect contact via thetransmission means that deliver the signals to the coils and the laserinterferometer position sensing system which then transmits sensedposition information to the controller which receives other commands toinitiate drive signals which result in movement of the XY stage 30.

With the known position of the XY stage 30 from the interferometersystem 92, drive signals are sent from the position control system 94 tothe appropriate drive coils, 42X, 42X′, 44Y and 44Y′ to drive the XYstage to a new desired position. The motion of the XY stage is sensed bythe interferometer system 92 and position sensors 98X and 98Y (see FIG.5), and the X follower 72 and Y follower 82 are driven by the drivemembers 77 and 87, respectively, to follow the XY stage. As illustratedin FIG. 5, the position sensor 98X detects a variation of the Ydirection space between the XY stage 30 and the X follower 72 andgenerates an electric signal representing the amount of space to theposition control system 94. The position control system 94 generates aproper drive signal for the drive member 77 on the basis of the Xposition information from the interferometer system 92 and the signalfrom the position sensor 98X.

Also, the position sensor 98Y detects a variation of X direction spacebetween the XY stage 30 and the Y follower 82 and generates an electricsignal representing the amount of space, and the drive member 87 isenergized on the basis of the Y position information from theinterferometer system 92 and the signal from the position sensor 98Y.

Yaw correction is accomplished by the pairs of linear motors which canbe used to hold or offset yaw, or the pairs of linear motors can changethe rotational position of the XY stage. The data from either or bothpairs of laser beams 40A/40A′ and 40B/40B′ are used to obtain yawinformation. Electronic subtraction of digital position data obtainedfrom measurement using the laser beams 40A and 40A′ or 40B and 40B′ isperformed or both differences are added and divided by two.

This invention allows the positioning function of the XY stage to beaccomplished faster than if XY guides were used. Reaction forces createdin moving the XY stage can be coupled away from the image forming opticsand reticle handling equipment.

This invention needs no precision X or Y guides as compared to a guidedstage, and precision assembly and adjustment of the wafer XY stage isreduced due to the lack of precision guides. The servo bandwidth isincreased because the linear motor forces in the XY axes act directly onthe wafer stage; they do not have to act through a guide system.

Forces from the XY linear motors can all be sent substantially throughthe center of gravity of the XY stage thereby eliminating unwantedmoments of force (torque).

With the X follower 72 and the Y follower 82 mounted and moved totallyindependently of one another, any vibration of a follower is notconveyed to the wafer XY stage or to the optical system when usingcommercially available electro-magnetic linear motors for the magneticcoupling between each of the followers 72 and 82 and the XY stage 30 andwith clearance between the coils and magnet drive tracks less than about1 mm. Additionally, with the arms of one of the followers spaced aboveand below the arms of the other follower, the vector sum of the momentsof force at the center of gravity of the XY stage due to the positioningforces of cooperating drive members is substantially equal to zero.

No connection exists between the XY stage and the follower stages thatwould allow vibrations to pass between them in the X, Y or θ degrees offreedom. This allows the follower stages to be mounted to a vibratingreference frame without affecting performance of the wafer stage. Forexample, if the reaction frame were struck by an object, the XY stageand the projection is optical system would be unaffected.

It will be appreciated by a person skilled in the art that if the centerof gravity is not equidistant between either of the two X drive coils oreither of the two Y drive coils, that appropriate signals of differingmagnitude would be sent to the respective coils to apply more force tothe heavier side of the stage to drive the XY stage to the desiredposition.

For certain applications the drive elements 42X/42X′ or 42Y/42Y′ of theactuator or magnetic coupling assembly for supplying electromagneticforce to the movable XY stage may be held stationary (see FIG. 5) in astatic position with respect to movement of the stage in either the X orY direction, respectively.

In the last of the explanation of this embodiment, referring to FIG. 1Cagain, the essential structure of the present invention will bedescribed. As illustrated in FIG. 1C, the XY stage 30 is suspended onthe flat smooth surface (parallel with the X-Y plane) of the stage base28 through the air bearings 36 having air discharge ports and vacuumpre-load ports and is movable in X,Y and θ direction on the stage base28 without any friction.

The stage base 28 is supported on the foundation (or ground, basestructure) 21 by the isolation blocks 20, arms 18, blocks 22, thevertical bars 26 and the horizontal bars 27. Each of the isolationblocks 20 is composed of a vibration absorbing assembly to preventtransmission of the vibration from the foundation 21.

Since FIG.1C is a sectional view of the XY stage 30 along a line throughthe drive coils 42X,42X′ in Y direction, the following description isrestricted about the X follower 72.

In FIG.1C, the drive coils 42X are disposed in a magnetic field of drivetrack (magnet array elongated in X direction) 78 mounted on the followerarm 74 and the drive coils 42X′ are disposed in a magnetic field ofdrive track 78′ mounted on the follower arm 74′.

The two arms 74,74′ are rigidly assembled to move together in Ydirection by the guide rails 69,69′ formed inside of the reaction frame61. Also, the guide rails 69,69′ restrict the movement of the two arms74,74′ in X and Z directions. And the reaction frame 61 is directlysupported on the foundation 21 by the four support posts 62independently from the stage base 28.

Therefore, the drive coils 42X(42X′) and the drive tracks 78 (78′) aredisposed with respect to each other to maintain a predetermined gap (afew millimeters) in Y and Z directions.

Accordingly, when the drive coils 42X,42X′ are energized to move the XYstage 30 in X direction, the reaction force generated on the drivetracks 78,78′ is transferred to the foundation 21, not to the XY stag30.

On the other hand, as the XY stage 30 moves in Y direction, the two arms74,74′ are moved in Y direction by the drive-member 77 such that each ofthe drive tracks 78,78′ follows respective coils 42X,42X′ to maintainthe gap in Y direction on the basis of the measuring signal of theposition sensor 98X.

While the present invention has been described with reference to thepreferred embodiment having a pair of X drive members or coils 42X and42X′ and a pair of Y drive members or coils 44Y and 44Y′, it is possibleto construct a guideless stage and with an isolated reaction frame inaccordance with the invention with just three drive members or linearmotors such as shown in FIGS. 6 and 7. As illustrated in FIG. 6, a pairof Y drive coils 144Y and 144Y′ are provided on the stage 130 and asingle X drive coil or linear motor 142X is mounted centered at thecenter of gravity CGI of the XY stage. The Y drive coils 144Y and 144Y′are mounted on the arms 184 and 184′ of the Y follower 182, and the Xdrive coil 144X is mounted on an arm 174″ of a X follower 172. Byapplying appropriate drive signals to the drive coils 142X and 144Y and144Y′, the XY stage can be moved to the desired XY positions.

Referring now to FIGS. 8-11, there is shown an alternative embodiment ofthe present invention which includes links between. the XY drive coils242X, 242X′, 244Y and 244Y′ and the attachment to the XY stage 30′.These connections include a double flexure assembly 300 connecting thedrive coil 244Y to one end of a connecting member 320 and a doubleflexure assembly 330 connecting the other end of the connecting member320 to the XY stage 30′. The double flexure assembly 300 includes aflange 302 connected to the coil 244Y. A clamping member 304 is attachedvia clamping bolts to the flange 302 to clamp therebetween one edge of ahorizontal flexible link 306. The other end of the flexible link 306 isclamped between two horizontal members 308 which are in turn integrallyconnected with a vertical flange 310 to which are bolted a pair offlange members 312 which clamp one edge of a vertical flexible member314. The opposite edge of the vertical flexible member 314 is clampedbetween a pair of flange members 316 which are in turn bolted to aflange plate 318 on one end of the connecting member 320. At the otherend of the connecting member 320 a plate 348 is connected to two flangemembers 36 which are bolted together to clamp one end of a verticalflexible member 344. The opposite edge of the vertical member 344 isclamped by flange members 342 which are in turn connected to a plate 340connected to a pair of clamping plates 338 clamping one edge of ahorizontal flexible member 336, the opposing edge of which is in turnclamped onto the XY stage 30′ with the aid of the plate 334. Thus, ineach of the double flexure assemblies 300 and 330 vibrations are reducedby providing both a horizontal and a vertical flexible member. In eachof these assemblies the vertical flexible members reduce X, Y and θvibrations and the horizontal flexible members reduce Z, tilt and rollvibrations. Thus, there are eight vertical flex joints for X, Y and θand eight horizontal flex joints for Z, tilt and roll.

As illustrated in FIG. 11, the coil 244Y is attached to a coil support245Y which has an upper support plate 246 attached thereto which ridesabove the top of the magnetic track assembly 288. Vacuum pre-load typeair bearings 290 are provided between the coil support 245Y and uppersupport plate 246 on the one hand is and the magnetic track assembly 288on the other hand.

In an operative example of the embodiment illustrated in FIGS. 8-11 theflexible members 306, 314, 344 and 336 are stainless steel 1¼″ wide, ¼″long and 0.012″ thick with the primary direction of flex being in thedirection of the thickness. In the embodiment illustrated members 306and 314 are mounted in series with their respective primary direction offlex being orthogonal to one another; members 344 and 336 are similarlymounted.

While the present invention has been described in terms of the preferredembodiment, the invention can take many different forms and is onlylimited by the scope of the following claims.

I claim:
 1. An exposure apparatus that transfers an image onto anobject, comprising: a support structure; an exposure device, supportedon the support structure, to expose the image onto the object; a stagemovably supported by the support structure; a reaction frame that isdynamically isolated from the support structure; and a drive, connectedat least partly to the reaction frame, to move the stage, wherein areaction force caused by the movement of the stage is transferredsubstantially to the reaction frame.
 2. An apparatus according to claim1, wherein the support structure and the reaction frame are supported ona foundation.
 3. An apparatus according to claim 2, wherein the supportstructure is mounted on the foundation with a block between the supportstructure and the foundation.
 4. An apparatus according to claim 3,wherein the block comprises a vibration absorbing assembly that preventstransmission of vibration from the foundation to the support structure.5. An apparatus according to claim 2, wherein the foundation is theground or a base structure.
 6. An apparatus according to claim 5,wherein the stage is located between the exposure device and thefoundation; and the drive has a first portion, located between theexposure device and the foundation, that is connected to the stage, anda second portion, located other than between the exposure device and thefoundation, that is connected to the reaction frame.
 7. An apparatusaccording to claim 6, wherein the support structure includes at leastthree spaced apart blocks on the foundation.
 8. An apparatus accordingto claim 6, wherein the first portion of the drive iselectromagnetically coupled to the stage.
 9. An apparatus according toclaim 6, wherein the exposure device includes a projection system thatprojects the image.
 10. An apparatus according to claim 9, wherein theprojection system optically projects the image.
 11. An apparatusaccording to claim 6, wherein the exposure device includes a mask holderthat holds a mask which defines the image.
 12. An apparatus according toclaim 6, wherein the reaction frame has at least one support post thatextends downward to rest on the foundation, and the second portion ofthe drive is connected to the at least one support post.
 13. Anapparatus according to claim 1, wherein the exposure device includes amask holder that holds a mask which defines the image.
 14. An apparatusaccording to claim 1, wherein the exposure device includes a projectionsystem that projects the image.
 15. An apparatus according to claim 14,wherein the projection system optically projects the image.
 16. Anapparatus according to claim 14, wherein the exposure device includes amask holder that holds a mask which defines the image.
 17. An apparatusaccording to claim 16, wherein the projection system is disposed betweenthe mask and the object.
 18. An apparatus according to claim 1, whereinthe stage is a wafer stage on which the object is supported.
 19. Anapparatus according to claim 1, wherein the stage is a guideless stagehaving no associated guide member to guide its movement.
 20. Anapparatus according to claim 19, wherein the support structure includesa base, and the guideless stage is two-dimensionally movable over asurface of the base on a bearing.
 21. An apparatus according to claim20, wherein the bearing is a non-contact bearing that supports theguideless stage.
 22. An apparatus according to claim 21, wherein thebearing comprises an air bearing.
 23. An apparatus according to claim21, wherein the bearing includes a magnet and a cooperating coil.
 24. Anapparatus according to claim 1, wherein the drive comprises a linearmotor.
 25. An apparatus according to claim 1, wherein the drive rotatesthe stage on an axis of the stage.
 26. An apparatus according to claim1, wherein the drive moves the stage in a two-dimensional plane,including movement in a first linear direction, a second lineardirection and a rotative direction on an axis of the stage.
 27. Anapparatus according to claim 1, wherein the drive includes a firstportion mounted on the reaction frame, and a second portion connected tothe stage and movable relative to the first portion.
 28. An apparatusaccording to claim 27, further comprising a drive mechanism that movesthe first portion.
 29. An apparatus according to claim 27, wherein thefirst portion comprises a drive track, and the second portion comprisesa drive coil.
 30. An exposure apparatus that transfers an image onto anobject, comprising a base having a surface and no guide member; a stagemovably supported by the base to move above the surface, the stagehaving no associated member to guide its movement on the base; a drivethat drives the stage in a two-dimensional plane including movement in afirst linear direction, a second linear direction and a rotativedirection about an axis of the stage; and a reaction frame that isdifferent from the base, wherein a reaction force caused by the movementof the stage is transferred to the reaction frame.
 31. An apparatusaccording to claim 30, wherein the stage is a wafer stage on which theobject is supported.
 32. An apparatus according to claim 30, wherein thedrive comprises a plurality of actuators.
 33. An apparatus according toclaim 30, wherein the drive includes a first portion connected to thereaction frame and a second portion connected to the stage and movablerelative to the first portion.
 34. An apparatus according to claim 30,further comprising a mask holder that holds a mask which defines theimage.
 35. An apparatus according to claim 30, further comprising aprojection system that projects the image.
 36. An apparatus according toclaim 35, wherein the projection system optically projects the image.